What is Fragile X?

Fragile X is the most common identifiable, inherited cause of intellectual disability. It is estimated to occur in 1 in 4000 males and 1 in 6000 females.
Fragile X syndrome is associated with varying degrees of intellectual disability. As it is a genetically inherited condition, when one child in a family is diagnosed with Fragile X, there are enormous implications for the parents and brothers and sisters of that child. Indeed there are implications for many other relatives of the wider family circle as they may also be carriers of, or affected by, the syndrome.

Both men and women can be carriers of Fragile X syndrome.

Why is it called Fragile X?

In 1991 the gene that causes Fragile X was identified. This gene, officially called FMR-1, is found at the tip of the X chromosome and shows as a ‘fragile’ site, that is, it looks as though it is broken off but not quite separated. It is this ‘fragile’ site on the X chromosome that gives its name to the syndrome.